Denver Broncos quarterback Drew Lock (3) looks to throw against the San Francisco 49ers during the second half of an NFL preseason football game, Monday, Aug. 19, 2019, in Denver. (AP Photo/David Zalubowski)

ENGLEWOOD | Two players made their long-awaited debuts as the Denver Broncos practiced on Tuesday: rookie quarterback Drew Lock and free agent cornerback Bryce Callahan.

Lock landed on injured reserve to start the season after spraining his right thumb during an exhibition game against San Francisco in mid-August. The Broncos will have to make a decision on his status by Dec. 3. If they don’t activate him by that date, he’ll stay on IR and his season will be over.

Lock is one of two players on IR that the Broncos have designated for a possible return this season. The other is wide receiver Tim Patrick (hand), who returned two weeks ago.

Callahan has remained on the 53-man roster while dealing with a right foot injury since July. It’s the same foot he broke last December before signing a three-year, $21 million free agent contract to follow Vic Fangio from the Chicago Bears to Denver.

In Callahan’s absence, the Broncos (3-6) have found a hidden gem in waiver wire pickup Davontae Harris, who’s helped the secondary post the league’s fourth-best defense behind only the 49ers (8-1), Patriots (8-1) and Bills (6-3).

QB Brandon Allen will make his first road start Sunday at Minnesota (6-3). Allen replaced Joe Flacco (neck) and led Denver over Cleveland 24-19 in his NFL debut before the Broncos’ bye last week.